This suggests OVs may boost various forms of immunotherapy, including tumor-specific bi-specific antibodies (BsAbs).<h4>Methods</h4>Our study investigated in vitro, how ONCOS-204, a variant of ONCOS-virus expressing the ligand of inducible T-cell co-stimulator (ICOSL), modulates the process of T cell activation induced by a BsAb. The gene discussed is ICOSLG; the disease is neoplasm.